You could merge schemas, object classes and attribute types from one schema project to another using the Merge Schemas wizard. To start the wizard choose Import > Merge Schemas from other Projects from the context menu of the Schema view.
The following wizard appears:
Check each schema, object class and/or attribute type from to merge to the current schema project and click on the Next button.
The second wizard page appears:
Select merge options.
|Replace unknown syntax||If checked, unknown syntaxes are replaced by Directory String syntax, and appropriate matching rules (caseIgnoreMatch, caseIgnoreSubstringsMatch) are set.||checked|
|Merge dependencies||If checked, dependent schema elements (super classes, super attribute types, may and must attributes) are also merged.||checked|
|Merge inherited attributes||If checked, must and may attributes that are not defined in the class hierarchy in the target schema are added to the merged object class.||checked|